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The U.S. auto industry is on track to sell upwards of 13.8 million vehicles in 2012, and both Ford (NYSE: F) and General Motors reported strong sales increases of 13% and 11%, respectively, in May. Even Toyota's sales jumped 87%, though that huge comparative jump occurred because of the earthquake and tsunami that devastated production last year.

While there's still strong demand out there, warm weather earlier in the year might have pulled some sales forward, and despite the robust numbers, Ford's shares have fallen 26% from their highs while GM is down by a third. Even Toyota has lost more than 12% from the 52-week peak it hit in March.

Get your motor runningOver on Motley Fool CAPS, the industry screener lists 55 stocks under "automotive," of which less than two dozen carry well-respected four- and five-star ratings. One of those that floats to the top is Westport Innovations (Nasdaq: WPRT) , the natural gas engine conversion manufacturer, which has seen its shares soar 46% over the past year, far outstripping the 6% gains of the S&P 500. And that's after the stock was cut in half from its March highs.

Part of the growth thesis in Westport has been the abundance of domestic natural gas and its low price. When oil is hitting $100 a barrel, natural gas that goes for just $2 or $3 per million BTUs is a significant discount. Prices will eventually rise as drillers cut back rigs and production, but there will always be a bias in favor of gas.

With Clean Energy Fuels (Nasdaq: CLNE) building out the infrastructure necessary to support a fleet of nat-gas cars, there's a large runway for Westport to take off. Yet the ramp is so broad that it's inviting competition, with engine maker Cummins acting as both a joint venture partner with Westport and as a competitor making its own natural gas engines.

Still, there's plenty of room for both. Nat gas has powered a fleet of vehicles in industrial uses -- forklifts are a prime example -- and Caterpillar (NYSE: CAT) is looking into converting its heavy equipment machinery by partnering with Westport to build out natural gas technology for off-road equipment, including mining trucks and even locomotives.

It's these partnerships that attract CAPS member keithelane, who notes that "Westport has done a great job of locking down several avenues for future success with Cummins, Ford, Volvo, Weichai, and now CAT." With the sell-off in its shares, he believes investors have an excellent entry point.

Westport remains my single best CAPScall, despite the recent volatility, but add the stock to the Fool's free portfolio tracker to keep tabs on future partnership deals it inks.

In the rearview mirrorOne highly rated stock that's gone in the other direction from Westport is auto-dimming mirror maker Gentex (Nasdaq: GNTX) , whose shares are down 23% over the past 12 months. Despite counting Ford, GM, and Chrysler as its primary North American customers, it faces mounting competition from Magna International and has seen the rate of growth slow in sales. But with two-thirds of its sales coming from international markets, there's a lot of growth still ahead as the industry regroups globally.

The big catalyst for Gentex, however, is the adoption of rear-camera displays, or RCDs, that promise to be a technological advance. The mirror maker's stock got crushed a few months back because it issued guidance that showed flat sales for 2012, and that was predicated on delays in implementing new regulations for U.S. carmakers.

Part of the problem for Gentex is the location of the display. The NHTSA says the cheapest spot to put the display is in a car's existing video screen. Gentex thinks the rearview mirror is best. Despite the high cost to the auto industry in terms of the number of lives saved -- industry analysts peg it at about $20 million per life -- it doesn't seem the regulators will abandon the rule, so Gentex ought to be able to cash in when they're finally implemented.

With 94% of the CAPS All-Stars rating Gentex betting it will outperform the broad market indexes, it appears they're looking out the windshield at what is to come and not in the rearview mirror of what has gone on before. Add the mirror maker to your own watchlist, then let me know in the comments section below or on the Gentex CAPS page if you agree that their view is not distorted.

The ball's in your courtGentex isn't the only American company eyeing growth in emerging markets. In fact, the Motley Fool's top analysts have identified a few American companies finding lucrative opportunities abroad. Learn more about these companies right now with our new free report, "3 American Companies Set to Dominate the World." It's completely free for Fool readers, but only for a limited time -- so grab your copy now.

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Rich has been a Fool since 1998 and writing for the site since 2004. After 20 years of patrolling the mean streets of suburbia, he hung up his badge and gun to take up a pen full time.

Having made the streets safe for Truth, Justice and Krispy Kreme donuts, he now patrols the markets looking for companies he can lock up as long-term holdings in a portfolio. So follow me on Facebook and Twitter for the most important industry news in retail and consumer products and other great stories.